chore: Deprecate memchr feature in favor of dep: syntax

The "memchr" feature does nothing on its own.

Author: DaniPopes

Cargo.toml

@@ -140,8 +140,11 @@ harness = false
 
 [features]
 default = []
-simd = ["memchr"]
+simd = ["dep:memchr"]
 testing-colors = []
 
+# Deprecated
+memchr = []
+
 [lints]
 workspace = true